Why was proportion important in Leon Battista Alberti’s architectural theory?

In Leon Battista Alberti’s architectural theory, proportion was the fundamental predetermining factor of beauty. He defined beauty, or pulchritudo, as a reasoned harmony of all parts within a body, structured so that nothing could be added, taken away, or altered without making the result worse.123

For Alberti, this harmony was not merely aesthetic but was rooted in mathematical laws comparable to those found in music. He believed that architectural beauty should be derived from harmonious proportions that resonate with a sense of order. By grounding his stylistic principles in this developed aesthetic theory, Alberti sought to create structures where the relationship between parts was clear and measured, allowing for an immediate and full comprehension of the building by the spectator.2314

His approach emphasized that beauty was an objective quality achieved through the perfect integration of structure, where the arrangement of parts was governed by a sense of decorum and mathematical precision. This focus on proportion helped differentiate the Renaissance style from the Gothic and established a standard for architectural excellence that influenced generations of architects.241